Extrude in same angle?
Option 1

If the face you are extruding from is planar one way to do this is to use a custom orientation which you can take from that face and use as a local coordinate system for future operations.



In the example I already had a "Transform Orientation" named Face, and Blender made a new one called "Face.001" so as not to override the old one.

Option 2

Select the edge you want to extrude, change the transform orientation in the tool below, to Normal. Hit Extrude, and press (X,Y, or Z) twice until you see an orientation line that matches the direction you want to translate the extrude edge in.